THE FOUR MOST COMMON STAGES TO HAVE AN ULTRASOUND.

DATING SCAN – 8-12 WEEKS

Routine dating scans are no longer supported by the Ministry of Health. If there are any clinical indications determined by your midwife or doctor that an early scan is necessary (such as a suspected miscarriage or ectopic pregnancy) it can be requested, otherwise current guidelines state that the first ultrasound of the pregnancy should ideally be offered when the gestational age is thought to be between 12 weeks and 13 weeks + 6 days.

FIRST TRIMESTER SCAN +/- NUCHAL SCREENING – 12 WEEKS

The purpose of this scan is to check for your baby’s heart beat (viability), confirm the estimated due date, confirm the number of babies and evaluate the baby’s health. In addition and only if requested we will also check the Nuchal translucency as part of the maternal serum screening (MSS1) for Downs Syndrome and other chromosomal abnormalities. This scan is performed between 12 weeks and 13 weeks + 6 days.

MSS1 FIRST TRIMESTER SCREENING

If after discussion with your midwife you decide to have first trimester screening for downs syndrome and other chromosomal abnormalities we will take one additional measurement on your baby. This measurement is of a small fluid area at the back of the baby’s neck called the nuchal translucency.

We send these measurements to LabPlus in Auckland where a blood sample from you is also sent. LabPlus then calculate the risk or chance that your pregnancy is affected with Downs Syndrome. Because this calculation is not carried out on site we are not able to give you the results straight away (on the day). LabPlus will contact your midwife with the results and she will discuss the results with you

MSS2 SECOND TRIMESTER SCREENING

If your first scan is performed after 13 weeks + 6 days you can still have screening for Downs Syndrome and other chromosomal abnormalities. This is done as a simple blood test. This is known as second trimester screening or MSS2.

For more information about first and second trimester screening click here https://www.nsu.govt.nz/pregnancy-newborn-screening/antenatal-screening-down-syndrome-and-other-conditions

First trimester screening is offered to all women, but you don’t have to have it, it is your choice.

ANATOMY SCAN – 20 WEEKS

This is a detailed ultrasound scan, usually carried out when you are 20 weeks pregnant. This scan checks for major physical abnormalities in your baby, although it can’t pick up every problem. So whilst a normal 20 week scan is very reassuring it cannot guarantee a healthy baby.

This scan usually takes around 30 minutes although it can take longer if the baby is in a difficult position or if a problem is detected.

The quality of the pictures we get depend on a number of factors including the position of the baby, the position, shape and structure of your womb, maternal BMI and the gestation of the pregnancy.

1. Position of the baby – sometimes babies just lie in awkward positions. It’s just one of those things and we will do our best to try and encourage it to move to enable us to do all our checks.
2. Your womb – every one of us is different, some wombs tilt forwards and some tilt backwards, sometimes these variations can make scanning a little harder and the pictures a little less clear.
3. Maternal BMI – ultrasound works by sending sound waves into the body and ‘listening’ to the echoes that come back. The more tissue the sound has to travel through to reach the baby, the less clear the image. We can usually get clear enough images to do the checks that we need to do but sometimes with larger ladies we have to ask you to come back when the baby is a little bigger to help us see more clearly.
4. Gestation of the pregnancy – ideally we like to do the anatomy scan at 20 weeks as this is the best time to do our checks for most women. To do the scan early means that the baby is smaller and it is harder to see the detail that we need to check and scanning too late in the pregnancy means that the baby is often very curled up and less likely to turn and move to show us what we need.

If for any of the reasons listed above we are unable to complete our checks on your baby we will arrange a follow up scan for you.

Fortunately most scans are normal, however some scans will show problems with the baby. Some of the problems we detect may resolve spontaneously during pregnancy, some may require treatment after the baby is born, or rarely a major problem that may affect the baby’s survival will be detected. If a problem is found this will be discussed with you and your midwife will be informed. If necessary your midwife will arrange appointments for you to see a specialist to discuss the long term implications for the health of your baby.

If you want to find out the sex of your baby, you can usually do so during the 20 week scan.

Tell the sonographer that you’d like to know your baby’s sex at the start of the scan. Be aware, though, that it’s not always possible for the sonographer to be 100% certain about your baby’s sex. For example, if your baby is lying in an awkward position, or if the image is not clear enough as discussed above.

Please also remember that the health of your baby is our priority and whilst we are happy to tell you the gender if we can see it is not the reason for the scan.

Although in theory it is sometimes possible to tell the sex of the baby at 12 weeks it is not our policy to do so as it is often difficult, time consuming and not as accurate as we would like.

GROWTH SCAN – 28 + WEEKS

Growth scans are performed routinely in twin pregnancies but are also sometimes requested by your midwife later in pregnancy if there is concern about the baby’s growth, position or the placental location.

This scan usually takes about 20 minutes.